The paper is intended to pursue the issue of relationship between error and fraud perceived as vices of will within the context of the legal transactions. In the general perspective, both are based upon the principles of individual autonomy and private freedom and in both cases the error that involved a party into a transaction can dramatically influence the validity of the latter. Meanwhile, regardless the common roots and common fundamental principles, each of them possesses its specific features and characteristics, meaningful for the theoretical elaboration of the doctrinal approaches as well as for the practical application of the respective legal provisions. Special attention has been paid to the issue of fraud by act of silence, referred to in the current version of the Civil Code of the Russian Federation as a result of the reforming of its provisions, whereby particular importance attracts the duty of disclosure.